Difference between voluntary and nonvoluntary muscles?

Voluntary muscles and nonvoluntary muscles, also known as skeletal muscles and smooth muscles, are two types of muscles in the human body. They are distinguished by their structure, location, function, and control.

Voluntary Muscles:

1. Structure: Voluntary muscles are composed of long, cylindrical, multinucleated muscle cells called muscle fibers. They have a striated appearance due to the regular arrangement of actin and myosin filaments.

2. Location: Voluntary muscles are primarily attached to bones and form part of the skeletal system. They are responsible for skeletal movements, such as limb movement, lifting objects, and locomotion.

3. Function: Voluntary muscles are under conscious control and can be contracted and relaxed at will. They are used for voluntary movements and can be precisely controlled and coordinated.

4. Control: Voluntary muscles are innervated by somatic motor neurons, which transmit signals from the central nervous system (brain and spinal cord) to the muscles. This allows us to consciously control and move our body parts.

Nonvoluntary Muscles:

1. Structure: Nonvoluntary muscles, also known as smooth muscles, consist of spindle-shaped, single-nucleated muscle cells. They have a smooth appearance due to the irregular arrangement of actin and myosin filaments.

2. Location: Nonvoluntary muscles are found in the internal organs, blood vessels, respiratory passages, digestive tract, and other structures. They are not part of the skeletal system.

3. Function: Nonvoluntary muscles are responsible for involuntary movements, such as digestion, peristalsis, blood flow regulation, pupil dilation, and constriction. They operate unconsciously and are not under direct voluntary control.

4. Control: Nonvoluntary muscles are innervated by the autonomic nervous system (sympathetic and parasympathetic divisions). This system controls involuntary functions without conscious thought.

In summary, voluntary muscles are attached to bones and are used for conscious, controlled movements. They are under the control of the somatic nervous system. Nonvoluntary muscles, on the other hand, are found in internal organs and are responsible for involuntary functions regulated by the autonomic nervous system.